组合油管最大下入深度计算新公式及其应用

New Formula and Its Application of Maximum Depth Calculation of Combined Tubing

在前人研究的基础上，考虑了浮力的影响，重新推导出组合油管最大下入深度计算新公式，并进行了实例计算和对比分析。分析结果表明以前计算出的最大下入深度偏低，实际最大下入深度应是其1．13倍，也即不考虑浮力会给油管最大下入深度计算带来11．5％的误差。因此，为利于准确地优化组合油管结构，必须考虑浮力的影响。此外，分析还表明，推导出的新公式是一个通用公式，它可以变形为单一油管的最大下入深度计算公式；由于考虑了井筒液体密度的影响，也可以变形为不考虑浮力时的计算公式，故该公式具有很强的适用性。最后，对该公式的应用进行了初步探讨，并得出了新的结论：对于组合油管而言，该公式只能为油管的优选提供初步方案；而最佳方案的确定，还需要通过分段计算各部分油管的实际抗拉安全系数来实现．从而为组合油管的优选提供了新方法。

Based on the tormer research, the influence of buoyancy is considered. The new formula for calculating the olaximum feeding depth of the combined oil pipe is derived, and embodiment calculation and comparison analysis are carried out. The analysis result shows the former maximum feeding depth is low, and the actual maximum feeding depth should be 1.13 times as tile former one. and the 11.5% error on tile calculation of the maximum feeding depth of the oil pipe caused by buoyancy is also noi considered. Thos, to accurately optimize the structure of combined oil pipe, the influence of buoyancy must be considered. In addition, the analysis also shows the new derived fbrmula is a general formula, and it can be changed into the fl^rmula tor calculating the maximum feeding depth of the single oil pipe. For the influence of the liquid density of the well hole is considered, the fornmla also can be changed into the calculation formula when the buoyancy is not considered, thus, the f^rmula has strong applicability. Finally, initial discussion is carried out to the formula, and a new conclusion is achieved. To the combined oil pipe, the fbrmula can only provide initial scheme for the preference of the oil pipe. The determination uf the best scheme needs to be realized by calculating the actual tensile safety coefficient of the oil pipe of each section, thus, the new method for the preference of the combined oil pipe is provided.